Electric selective signaling system



Nov. 30, 1948. 1.. R. FROST ELECTRIC SELECTIVE SIGNALING SYSTEM 2 Sheets-Sheet 1 Filed Jan. 8, 1947 NOV. 30, 1948. v R, FRQST 2,454,967

ELECTRIC SELECTIVE SIGNALING sy s'r su Filed Jan, 8, 1947 2 Sheets-Sheet 2' RECEIVE T0 Mame Fae OEIIIIVG 501v Ml/EELJU I I/f/EELII I 45 7 44 RECEIVE Patented Nov. 30, 1948 U NITED STAT Application .1! anu'ary 8, 1947, Serial No. 720,841 'In Great Britain June 6, I944 scans. (01. m ss This invention has for its object to provide an improved form of sender and receiver for an electric selective signalling system of the kind in which manua-l setting of a control element of the sender to one or a series of alternative positions efiects movement to corresponding position of a follower element of the receiver, sothat the position of the follower element will always c'onform'jwith that of the control element. 7

The sender and receiver according to the in} vention are reversible in two senses. Firstly they are reversible as regards function, i, e. they can be used at willeitherto send or to're'ceive signals, the same element of the device functioning as control element or as follower element according as to whether signals are being trans mittd or received. Secondly they are reversible as regards direction of movement, he. the control element of the sender canbe giveneither a forward movement or a reverse movement which will be faithfully copied by the follower element of the receiver. H H Y I The invention providesja mechanism, which is operable at will to function either as a sender or as a receiver for an electric selective signalling system of the above kind, and which comprises a differential gear, having two coaxial sun wheels and a planet wheel meshingwithboth of said sun wheelsand mounted for bodily rotation about thecommon axis of said sun wheel's the planet wheel being coupled to the control element so as to be moved forwardly or in a reverse direction in relation to the sun wheels according to the movement of the control element, a set of keys or equivalent manipulative members operatively connected to the control element, each key servme, when operated, to move the control element to a definite position allotted to that key, means associated with the sun Wheels for constraining them, on movement of the planet wheel as aforesaid, to execute a relative rotation which is determined in direction and extent by the direction and extent of said movement of the planet wheel, and a two-way electrical unit which is effective on the one hand, in response to actuation ofthe setting means aforesaid, to produce a variable signal for actuating a distant receiverwhichis representative of the direction and extent of said relative rotation of the sun wheels, and on the other hand to produce, in response to a signal received from a distant sender, relative rotation of said sun wheels, which is determined as regards both direction and extent by said signal,

The movement imparted to the planet wheel bmpera im Q me. e t ng me n ma be ith a rotational movement about its axis, or a bodily 2 movement of rotation about the commQny axis. h s W e ar pref ably. sn ma ylsta tic-nary, and if so the sun wheels are constrained to execute theabove-mentioned relative move- 5 ment by associating vvithhthemrestraining devices, e. g. oi' the pawl and ratchet type, ar-

a d n t eh jm rjcase t perm is nlvdof movement of the sun wheels inthje same directioira n he att rmca e to perm t o lxo movement of the sun wheels in opposite direc- I do not, however, exclude the possibility oi dep eting. ,consta t r ta n u eela, dli ue e s. h idri eni e h am direction when operation of the setting means ai afl iba l ne ,rzheels b u i s x a d. ntepe e si ttc ieeei lltehes ta on i t settin eeaee.efi ei ilqedi r.ro at n Pith P an wheel about the common axis of the sun wheels.

Wl eta he em whe e ei r v n. he. r v ac as described later a s the constrainin'gmeans for producing the required relative rotationo f the ,c in u ease of stationary slin' wh 1 I 1 p when thejmech- I oper I timin t t aaisiii is'in useasa" re t- 0. 9 relat ve. s

pulsesfdetermin h I flativerota 10 [of the Wheels, and the s'e'l e'noids and "plli'rlgers operating alternatively, when the mechanism is inuse as a receiver and aceorcimg to the "direction of relative rotation of the sunwheels "of the distant sender, to efiect elativerotaticn of the associated sun Wheels to an extnt'det'rmined by. the number of impulses in..the signal: received from the distant sender. This method isconven'ient because it. permits of transmission" of signals: by means of; electrormagneticradiation using alternative radiqjrequency channels or, as later described by means; oi a singlev l e usin an: .ea 1 ;.t e i r -v c h le it: wi en u ethat th rece ver will r mai riais n h the sender, o 1 52a; a the..iQen t ea. i k. .i as l am-t h we er ie, m nis. tep pi iha e iv r s u fisiab h dj a ter aifa t has v. ire their 6% receiver may be connected by a" circuit which one or more signals may have includes a pair of resistances or the like, one associated with the sender and the other with the receiver, the circuit being arranged to develop an out-of-balance current when they are out of balance, the two-way electrical unit associated with each mechanism comprising means operating, when the mechanism is acting as a sender, to vary the associated resistance by an amount representative of the direction and extent of movement of the sun wheels of said mechanism, and means operating, when the mechanism is acting as a receiver and in response tothe out-of-balance current in the circuit, to eifect relative rotation of the sun wheels of the mechanism to restore the balance of said resistances.

With this arrangement, even if a fault has developed, the receiver must of necessity come into step, by rebalancing the resistances, when the faul is put right. Where resistance are employed as the balancing elements direct or alternating current may be used in the circuit. Where alternating current is used or the connection between sender and receiver is by electro magnetic radiation, capacities or inductances can be used as the balancing elements, the local circuits associated with the sender and receiver reacting so that transmission ceases when the elements are balanced.

Some practical embodiments of the invention will now be described in detail by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a side elevation of a differential gear unit for use in a sender or receiver according to the invention,

Fig. 2 is a section on the line IIII in Fig. 1,

Fig. 3 is a diagrammatic perspective view of a sender or receiver employing the diiferential gear unit of Fig. 1,

Fig. 4 is a circuit diagram to illustrate the use of mechanism as shown in Fig. 3,

Fig, 5 is a diagrammatic perspective view showing an alternative form of sender or receiver, and

Fig. 6 is a circuit diagram to illustrate the use of mechanism as shown in Fig. 5.

Like references indicate like parts throughout the figures. In Figs. 4 and 6 parts associated with the receiver are differentiated from the same parts of the sender by the addition of the letter a to the reference characters.

Referring first or all to Figs. 1 and 2, the differential gear unit comprises a pair of coaxial sun wheels Ill, II rotatably mounted on a shaft I2 journalled in a supporting framework I3. To the sun wheel It is fixed a ratchet wheel I4 and to the sun wheel III is fixed a ratchet wheel I5. A pawl I8 permits the ratchet wheel I4 and associated sun wheel to rotate only in the clockwise direction as seen in Fig. 2, and a pawl [1 permits the ratchet wheel l5 and associated sun wheel to rotate in the anti-clockwise direction only as seen in Fig. 2. Meshing with the two sun wheels is a planet wheel !8, which is freely rotatable on a stud It projecting from a boss pinned to the shaft I2 by a screw 2 I.

Referring now to Fig. 3, the shaft 12 in this case constitutes the control element, when the mechanism is used as a sender, which serves to effect variable but controlled relative rotation of the sun wheels under the control of a set of manually operable keys 22. When the mechanism is used as a receiver the shaft I2 will act as a follower element, to take up a position corresponding to that of the shaft of the sender, this movement being derived from relative rotation of the sun wheels of the receiver under the control of the electrical signal as later described. The shaft E2 of the receiver will be utilised for setting any desired mechanism, e. g. the type wheel of a teleprinter, into a position corresponding to and determined by the setting of the keys of the sender.

As shown in Fig. 3, the shaft I2 carries a flat plate 23 and the keys 22 have at their lower ends plates 24 mounted at diiferent angles to the stem of the key. When any given key is depressed, its plate 24- will press on the plate 23 and so rotate the plate 23 and shaft I2 until the two plates are parallel. The extent and direction of the rotation of the shaft I2 will thus depend upon which of the keys has been depressed.

Rotation of the shaft I2 causes bodily rotation of the planet wheel I8 about the common axis of the sun wheels. If the shaft I2 rotates clockwise as seen from the right in Fig. 3, the sun wheel ID will be prevented from following owing to the pawl IE5 associated with its ratchet wheel I4 and the planet wheel will roll on the stationary sun wheel lil rotating the sun wheel II and ratchet I5 clockwise. At each step of clockwise rotation of the sun wheel II and ratchet I5, the pawl I1 will be clicked up by the ratchet teeth to make contact with a spring contact 26. A series of im pulses will thus be caused in a circuit associated with contact 26, the number of impulses being determined by the extent of rotation of the shaft l2.

Similarly anti-clockwise rotation of shaft I2 as seen from the right in Fig. 3, will result in the sun wheel iI remaining stationary and the sun wheel It turning anti-clockwise and imparting through the pawl I6 and cooperating contact 25 the appropriate number of impulses to the circuit including contact 25.

Associated with the ratchets I4, I5 are solenoids 2T, 28 respectively. Each solenoid surrounds a plunger 29, carrying a spring pawl 30 engaging the teeth of the associated ratchet, and normally held extended by a spring 3I. Each time one of the solenoids receives an impulse from a distant sender, its plunger is retracted to move the associated ratchet by one step.

As shown in Fig, 4, parallel circuits are taken from earth, through reversed batteries 32, normally open contacts 25, 26 and a rectifier 33 to the single line 34; leading from the sender to the receiver. The solenoids 21, 28 are connected in parallel between earth and the rectifier 33.

An earthing switch 84 is associated with the reversed batteries 32 and earthing switches are associated with the solenoids. When the mechanism is to be used as a sender, switch 84 is closed and switches 35 are open (see the left hand side of Fig. 4). When it is to be used as a receiver, switch 8 3 is open and switches 35 are closed (see the right hand side of Fig. 4)

As already explained, the direction of rotation of the shaft i2 determines whether contacts 25 or 75.6 are closed and the extent of rotation of shaft I2 determines the number of impulses transmitted. When contacts 25 are closed, say three times, by rotation of sun wheel it] through three steps, current is passed through the rectifiers to solenoid Zi associated with sun wheel II] of the receiver. This causes sun wheel Ill to move three steps and rotate the follower shaft of the receiver by an equal amount and in the same direction as the control shaft of the sender. The same result takes place, of course, when the direction of rotation of the control shaft is such as movement of the follower shaft of the receiver.

The armatures could of course be arranged to control escapement mechanisms associated with 'the sun Wheels instead of elfecting'positive-operation' thereof illustrated. I

In the embodiment of Fig. 5, the 'pawls 16,11 are arranged to prevent movement of the normally stationary sun wheels l0, H in the same direction. In this case the control movement is imparted to the differential unit, under the control of keys 22, by causing the planet wheel- I8 to rotate about its axis. To this end the planet wheel carries a pinion 55 engaging a rack 36 formed on a part 38 which is rotatable about and movable along the axis of shaft l2 within the confines of a; control bar'31. The control-bar 31 thus partakes of the sliding movement of the part 38 in relation to the shaft l2. The control bar 31 is formed with'a V-d'epresslon -39 for engagement of the keys, so that the longitudinal position of the control bar in relation to the shaft [2, and consequently the direction and extent of the rotation of the planet wheel l8 about its axis, are determined by the selected key. It will be understood that according to the direction of movement of the control bar, one or other of the sun wheels will be held stationary by its pawl, and the other will rotate.

The effective controlling element of the sender and corresponding follower element of the receiver is, in this case, constituted by the bar 31 which carries a contact 40 cooperating with a resistance 4|.

As shown in the circuit diagram in Fig. 6, the resistances 4|, 4| of the sender and receiver are cross connected, and the contacts 40, 40 are normally in a position such that the resistances are in balance, i. e. R+r1=R1+r so that equal currents flow through the upper and lower limbs of the two-pole relays 42, 42 When however the control bar 31 of the sender takes up a new position, the resistances are thrown out of balance, and the current through the upper coils of relays 42, 42 becomes greater or less than that flowing through the lower coils. The pivoted armatures 43, 43 of the relays therefore move to connect in circuit lines 44, 4 or lines 45, 45*. These, when connected in circuit energize electric motors for rotating the sun wheels of the associated mechanisms, the direction of relative rotation being determined by which pair of lines is in circuit. Movement thus imparted to the receiver continues until its contact 4|) has moved, as above described with reference to Fig. 5, to rebalance the resistances.

Switches 46, #6 are in the position shown when the left hand unit is acting as the sender, and lines 44, 45 will be earthed when connected in circuit and will not therefore actuate their associated electromagnetic devices. When the right hand unit is to act as sender, the switches 46, 46 are reversed, and lines 44, 45 Will be operative, when placed in circuit, to actuate their electromagnetic devices, lines 44 45 being then earthed.

I am aware that an electric signalling system has been proposed having a sender (which can also operate as a receiver) comprising a handle which is movable in either direction from a neutral position to establish one of two alternative circuits. The circuit so established operates through an electromagnet, to free one of the two sun wheels of a difierential gear for movement under the influence of an sc apeiherit; Thi's 'sjiiii wheel dl'iv'esthe planet wheel, and member connected thereto intime breaks the circuit again, the movementjpermittea"t the sun wheel beingpr'eeortieriar'tothe movement of the handle. As the sun wheel rotates electric signals are emitted to cause thecorrespondi'ng sun wheel of the receiver to execute a correspondingmovement. When the apparatus 'is actlng as a receiver, one of two eiectromagnas is energized by the sender to permit thecorre'sponding'sun wheel to rrioveundr the action of the escapement. This mechanism differs from that according to the invention in that no movement is communicated "to the planet wheel by the setting movement of the handle, which serves only to free one of the sun wheels for escapement movement. Nor i's' aset'of keys' orthe equivalent provided, by the selection of any of one of which a desired corresponding movement may be imparted to the receiver.

WhatI claimas my invention and desire to secure by Letters Patent is:

1. A mechanism, operable at will to function either as a sender or as a receiver for an electric selective signalling system of the kind specified, and comprising a, differential gear, having two coaxial sun wheel-s and a planet wheel meshing with both of said sun wheels and mounted for bodily rotation about the common axis of the sun wheels, the planet Wheel being coupled to the control element so as to be moved forwardly or in a reverse direction in relation to the sun wheels according to the movement of the control element, a set of keys or equivalent manipulative members operatively connected to the control element, each key serving, when operated, to move the control element to a definite position allotted to that key, means associated with the sun wheels for constraining them, on movement of the planet wheel as aforesaid, to execute a relative rotation which is determined in direction and extent by the direction and extent of said movement of the planet wheel, and a two-way electrical unit which is effective on the one hand, in response to actuation of the setting means aforesaid, to produce a variable signal for actuating the distant receiver which is representative of the direction and extent of said relative rotation of the sun wheels, and on the other hand to produce, in response to a signal received from a distant sender, relative rotation of said sun wheels which is determined as regards both direction and extent by said signal.

2. A mechanism as claimed in claim 1, in which the sun wheels are normally stationary, in which operation of the setting means effects rotational movement of the planet wheel about its axis, and in which the constraining means restrain the sun wheels against rotation in the same direction.

3. A mechanism as claimed in claim 1, in which the sun wheels are normally stationary, in which operation of the setting means effects bodily rotation of the planet wheel about the common axis of the sun wheels, and in which the constraining means restrain the sun wheels against rotation in opposite directions.

4. A mechanism as claimed in claim 1, wherein the sun wheels are normally stationary, operation of the setting means effecting bodily rotation of the planet wheel about the common axis of the sun Wheels and the constraining means restraining the sun wheels against rotation in opposite .directions, and wherein the two-way electrical unit comprises a make and break device and a 0 solenoid and plunger associated with each sun wheel, the make and break devices operating alternatively, when the mechanism is in use as a sender and according to the direction of relative rotation of the sun Wheels, to transmit a signal by making or breaking a circuit, said signal consisting of a series of impulses determined in number by the extent of relative rotation of the sun wheels, and the solenoids and plungers operating alternatively, when the mechanism is in use as a receiver and according to the direction of relative rotation of the sun wheels of the distant sender, to effect relative rotation of the associated sun Wheels to an extent determined by the number of impulses in the signal received fromv the distant sender.

5. The combination of a pair of mechanisms as claimed in claim 1, in which the sun wheels are normally stationary, operation of the setting means effecting rotational movement of the planet wheel about its axis and the constraining means restraining the sun wheels against rota- 8 tion in the same direction, one of said mecha' nisms constituting a sender and the other constituting a receiver, of a circuit connecting said mechanisms which includes a pair of resistances, one associated with the sender and the other with the receiver, the circuit being arranged to develop an out-of-balance current when they are out of balance, the two-way electrical unit associated with each mechanism comprising means operating, when the mechanism is acting as a sender, to vary the associated resistance by an amount representative of the direction and extent of movement of the sun wheels of said mechanism, and means operating, when the mechanism is acting as a receiver and in response to the out-ofbalance current in the circuit, to effect relative rotation of the sun wheels of the mechanism to restore the balance of said resistances.

LESLIE RICHARD FROST.

No references cited. 

